Apparatus for discriminating optical recording medium and method for discriminating optical recording medium

ABSTRACT

It is an object of the present invention to provide an apparatus for discriminating an optical recording medium and a method for discriminating an optical recording medium which can reliably discriminate the kind of an optical recording medium even in the case where the optical recording medium to be discriminated is warped. 
     The apparatus for discriminating an optical recording medium according to the present invention includes a first electrode  11 , a second electrode  12 , an alternating current signal generation circuit  13  for applying an alternating current signal A to the first electrode  11 , a detection circuit  14  for detecting the level of an alternating current signal B appearing at the second electrode  12 , a supporting mechanism  16  for supporting the first electrode  11  and the second electrode  12 , a driving mechanism  17  for vertically moving the supporting mechanism  16 , and a control circuit  15  for controlling the operations of the alternating current signal generation circuit  13  and the detection circuit  14  and the driving mechanism  17.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for discriminating anoptical recording medium and a method for discriminating an opticalrecording medium, and particularly, to an apparatus for discriminatingan optical recording medium and a method for discriminating an opticalrecording medium which can reliably discriminate the kind of an opticalrecording medium.

DESCRIPTION OF THE PRIOR ART

Optical recording media such as the CD, DVD and the like have beenwidely used as recording media for recording digital data and compatibledrives capable of reproducing data recorded in different opticalrecording media such as the CD, DVD and the like or recording andreproducing data therein and therefrom have recently been activelydeveloped.

Particularly, next-generation type optical recording media having largedata recording capacity and an extremely high data transfer rate haverecently been actively developed and it is expected that the kinds ofoptical recording media will further increase.

In such a compatible drive, it is necessary to discriminate the kind ofan optical recording medium set therein but since the shapes of thesedifferent kinds of optical recording media are standardized, it isimpossible to discriminate the kind of an optical recording medium settherein based on the shape thereof.

Therefore, a compatible drive is generally constituted so as todiscriminate the kind of an optical recording medium set therein byactually projecting a laser beam onto the optical recording medium settherein and judging whether or not a normal signal can be reproduced.

For example, a compatible drive capable of reproducing data recorded inboth CD and DVD is constituted so that when a distance between a lightincidence plane and a recording layer (reflective layer) is measured byconducting focus searching and it is judged that the distance betweenthe light incidence plane and the recording layer (reflective layer) isabout 1.1 mm, a laser beam having a wavelength of 780 nm for a CD isselected and that when it is judged that the distance between the lightincidence plane and the recording layer (reflective layer) is about 0.6mm, a laser beam having a wavelength of 650 nm for a DVD is selected.

However, in the case of discriminating the kind of an optical recordingmedium by conducting focus searching in this manner, a long time isrequired for discriminating the kind of the optical recording medium anda long period is required between the time when the optical recordingmedium is set in the drive and the time when data can be actuallyrecorded in or reproduced from the optical recording medium.

Therefore, Japanese Patent Application Laid Open No. 10-143986 proposesa method for discriminating an optical recording medium by providing anelectrode in a tray of a drive and applying an alternating currentsignal to the electrode, thereby discriminating the kind of an opticalrecording medium placed on the tray.

However, since the method disclosed in Japanese Patent Application LaidOpen No. 10-143986 uses an electrode fixed to the tray, thediscriminating accuracy is lowered as described below when the opticalrecording medium to be discriminated is-warped.

FIG. 10 is a schematic cross-sectional view showing a tray provided withan electrode for detection that is used in Japanese Patent ApplicationLaid Open No. 10-143986.

As shown in FIG. 10, the tray 1 includes a first setting portion la onwhich an optical recording medium having a diameter of 120 mm is to beplaced and a second setting portion 1 b which is provided at a centralportion of the first setting portion 1 a and on which an opticalrecording medium having a diameter of 80 mm is to be placed andelectrodes 2, 3 are provided in the second setting portion 1 b.

Further, a shoulder portion 4 a is provided on the outer circumferentialportion of the first setting portion la so that when an opticalrecording medium having a diameter of 120 mm is placed on the tray 1,the optical recording medium is held on the shoulder portion 4 a.

Similarly, a shoulder portion 4 b is provided on the outercircumferential portion of the second setting portion 1 b so that whenan optical recording medium having a diameter of 80 mm is placed on thetray 1, the optical recording medium is held on the shoulder portion 4b.

Therefore, when an optical recording medium is placed on the tray 1, therecording surface of the optical recording medium (which in the case ofan optical recording medium having a diameter of 120 mm is a region inwhich data are recorded that corresponds to that of the light incidenceplane and has an inner diameter of 50 mm and an outer diameter of 117mm) is kept from being brought into direct contact with the tray 1,thereby preventing the recording surface of the optical recording mediumfrom being damaged.

FIG. 11 is a schematic cross-sectional view showing the state of anoptical recording medium having a diameter of 120 mm placed on the tray1, wherein FIG. 11 (a) shows the state where the optical recordingmedium is warped in one direction and FIG. 11 (b) shows the state wherethe optical recording medium is warped in the other direction. In FIGS.11 (a) and (b), the warpage of the optical recording medium isexaggerated.

As apparent from FIGS. 11 (a) and (b), in the case where an opticalrecording medium is warped in the one direction, distances between theelectrodes 2, 3 for detection provided in the tray 1 and a conductivelayer(s) such as a reflective layer included in the optical recordingmedium become longer than that in the case where the optical recordingmedium is not warped and, on the other hand, in the case where anoptical recording medium is warped in the other direction, the distancesbetween the electrodes 2, 3 for detection provided in the tray 1 and aconductive layer(s) such as a reflective layer included in the opticalrecording medium becomes shorter than that in the case where the opticalrecording medium is not warped. As a result, when an alternating currentsignal is applied to one of the electrodes 2, 3, the level of the signalobtained from the other electrode 2, 3 depends upon whether or not theoptical recording medium is warped and in which direction the opticalrecording medium is warped and, therefore, there arises a risk of thedecrease in discriminating accuracy.

Although this problem is not so serious in the case of discriminating aCD, DVD or other optical recording media having different focusdistances, it becomes very serious in the case of discriminating opticalrecording media whose focus distances are the same.

In the case of discriminating optical recording media that differ littlein the distance between the light incidence plane and a conductive layersuch as a reflective layer, for example, in the case where a DVD inwhich data are to be recorded in one layer on one side and a DVD inwhich data are to be recorded in two layers on one side are to bediscriminated, the results of discrimination are greatly affected bychanges in detection signals caused by the warpage of the opticalrecording media.

It is particularly worthy of note that there are being developednext-generation type optical recording medium constituted so as to beirradiated with a laser beam having a wavelength equal to or shorterthan 450 nm via a light transmission layer disposed opposite to asubstrate using an objective lens having a numerical aperture equal toor smaller than 0.7. It is therefore expected that a plurality kinds ofnext-generation type optical recording media that differ only slightlyin the thickness and material of the light transmission layers will comeinto practical use. In the case where these next-generation type opticalrecording media are discriminated using the method disclosed in JapanesePatent Application Laid Open No. 10-143986, the results ofdiscrimination are very greatly affected by changes in detection signalscaused by warpage of the optical recording media.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide anapparatus for discriminating an optical recording medium and a methodfor discriminating an optical recording medium which can reliablydiscriminate the kind of an optical recording medium.

It is another object of the present invention to provide an apparatusfor discriminating an optical recording medium and a method fordiscriminating an optical recording medium which can reliablydiscriminate the kind of an optical recording medium even in the casewhere the optical recording medium to be discriminated is warped.

It is a further object of the present invention to provide an apparatusfor discriminating an optical recording medium and a method fordiscriminating an optical recording medium constituted so as to beirradiated with a laser beam from a side opposite to a substrate, whichcan reliably discriminate the kind of an optical recording medium.

The above objects of the present invention can be accomplished by anapparatus for discriminating an optical recording medium comprising atleast a first dielectric layer, a second dielectric layer and aconductive layer formed between the first dielectric layer and thesecond dielectric layer, the apparatus for discriminating an opticalrecording medium comprising a detecting section provided with anelectrode, a first means for applying a signal for detection to theelectrode and a second means for bringing the detecting section intocontact with a surface of the first dielectric layer.

According to the present invention, since the kind of an opticalrecording medium can be discriminated by causing the second means tobring the detecting section into contact with the surface of the firstdielectric layer and applying a signal for detection to the electrodewhile the detecting section is in contact with the surface of the firstdielectric layer, it is possible to reliably discriminate the kind of anoptical recording medium even in the case where the optical recordingmedium is warped.

In a preferred aspect of the present invention, the detecting sectionfurther comprises a protective layer for covering a surface of theelectrode and the second means is constituted so as to bring theprotective layer of the detecting section into contact with the surfaceof the first dielectric layer.

According to this preferred aspect of the present invention, since thedetecting section further comprises a protective layer for covering asurface of the electrode, it is possible to effectively prevent thesurface of the first dielectric layer from being damaged when thedetecting section is brought into contact with the surface of the firstdielectric layer.

In a preferred aspect of the present invention, the second means isconstituted so as to set the detecting section apart from the surface ofthe first dielectric layer prior to rotating an optical recordingmedium.

According to this preferred aspect of the present invention, since thedetecting section is set apart from the surface of the first dielectriclayer prior to rotating an optical recording medium, it is possible toreliably prevent the detecting section from being brought into contactwith and damaging the surface of the first dielectric layer during therotation of an optical recording medium.

In a further preferred aspect of the present invention, the detectingsection is provided in the tray of a drive and the second means isconstituted so as to move the detecting section in synchronism withdischarge and accommodation of the tray.

According to this preferred aspect of the present invention, since thedetecting section is provided in the tray of a drive, it is possible toshorten time required for actually recording data in or reproducing datafrom the optical recording medium after the optical recording medium isset in the tray.

In a further preferred aspect of the present invention, the firstdielectric layer is constituted as a light transmittance layer and thesecond dielectric layer is constituted as a substrate.

In a further preferred aspect of the present invention, the electrode isconstituted by a shaft of a roller of a slot-loading mechanism.

The above objects of the present invention can be also accomplished by amethod for discriminating an optical recording medium comprising atleast a first dielectric layer, a second dielectric layer and aconductive layer formed between the first dielectric layer and thesecond dielectric layer, the method for discriminating an opticalrecording medium comprising steps of bringing a detecting section havingan electrode into contact with a surface of the first dielectric layerand applying a signal for detection to the electrode, therebydiscriminating the kind of the optical recording medium.

According to the present invention, since the kind of an opticalrecording medium is discriminated by bringing a detecting section havingan electrode into contact with a surface of the first dielectric layerand applying a signal for detection to the electrode while the detectingsection is in contact with the surface of the first dielectric layer, itis possible to reliably discriminate the kind of an optical recordingmedium even in the case where the optical recording medium is warped.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an apparatus for discriminating anoptical recording medium that is a preferred embodiment of the presentinvention.

FIG. 2 is a diagram showing the structure of a detecting section,wherein FIG. 2( a) is a schematic perspective view showing a detectingsection and Figure (b) is a schematic cross-sectional view taken along aline A—A in FIG. 2( a).

FIG. 3 is a schematic cross-sectional view showing a drive.

FIG. 4 is a set of schematic cross-sectional views showing various kindsof optical recording media, wherein FIG. 4( a) is a schematiccross-sectional view showing a CD type optical recording medium, FIG. 4(b) is a schematic cross-sectional view showing a DVD type opticalrecording medium and FIG. 4( c) is a schematic cross-sectional viewshowing a next-generation type optical recording medium.

FIG. 5 is a flow chart of a method for discriminating an opticalrecording medium using an apparatus for discriminating an opticalrecording medium.

FIG. 6 is a schematic cross-sectional view showing the state where adetecting section of an apparatus for discriminating an opticalrecording medium is in contact with a light incidence plane of anoptical recording medium.

FIG. 7 is a diagram showing a circuit formed between a first electrodeand a second electrode.

FIG. 8 is a schematic cross-sectional view showing one example of amethod for mounting an apparatus for discriminating an optical recordingmedium on a data recording and reproducing apparatus (drive), whereinFIG. 8( a) shows the state where a tray is discharged from a main bodyand FIG. 8( b) shows the state where a tray is accommodated in the mainbody.

FIG. 9( a) is a schematic longitudinal cross-sectional view showinganother example of a method for mounting an apparatus for discriminatingan optical recording medium on a data recording and reproducingapparatus (drive) and FIG. 9( b) is a schematic cross-sectional viewtaken along a line A—A in FIG. 8( a).

FIG. 10 is a schematic cross-sectional view showing a tray provided withan electrode for detection in a conventional apparatus fordiscriminating an optical recording medium.

FIG. 11 is a schematic cross-sectional view showing the state where anoptical recording medium is placed on the tray, wherein FIG. 11( a)shows the state where an optical recording medium is warped in onedirection and FIG. 11( b) shows the state where an optical recordingmedium is warped in the other direction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be describedwith reference to accompanying drawings.

FIG. 1 is a block diagram showing an apparatus for discriminating anoptical recording medium that is a preferred embodiment of the presentinvention.

As shown in FIG. 1, an apparatus 10 for discriminating an opticalrecording medium that is a preferred embodiment of the present inventionincludes a first electrode 11, a second electrode 12, an alternatingcurrent signal generation circuit 13 for applying an alternating currentsignal A to the first electrode 11, a detection circuit 14 for detectingthe level of an alternating current signal B appearing at the secondelectrode 12, a supporting mechanism 16 for supporting the firstelectrode 11 and the second electrode 12, a driving mechanism 17 forvertically moving the supporting mechanism 16, and a control circuit 15for controlling the operations of the alternating current signalgeneration circuit 13 and the detection circuit 14 and the drivingmechanism 17.

A table 15 a is provided in the control circuit 15 and a detectingsection 18 is constituted by the first electrode 11, the secondelectrode 12 and the supporting mechanism 16 for supporting the firstelectrode 11 and the second electrode 12.

FIG. 2 is a diagram showing the structure of the detecting section 18,wherein FIG. 2( a) is a schematic perspective view showing the detectingsection 18 and Figure (b) is a schematic cross-sectional view takenalong a line A—A in FIG. 2( a).

As shown in FIG. 2( a), the supporting mechanism 16 is constituted by anarm 16 a adapted to be vertically moved by the driving mechanism 17 anda plate-like electrode mounting section 16 b provided at the tip endportion of the arm 16 a.

The first electrode 11 and the second electrode 12 are mounted on theelectrode mounting section 16 b and, as shown in FIG. 2( b), thesurfaces of the first electrode 11 and the second electrode 12 arecovered with a protective layer 19.

The protective layer 19 serves to prevent the first electrode 11 and thesecond electrode 12 from being corroded and also prevent the firstelectrode 11 and the second electrode 12 from coming into contact with arecording surface of an optical recording medium, thereby preventing therecording surface of the optical recording medium from being damaged bythe first electrode 11 and the second electrode 12.

Therefore, it is necessary for the protective layer 19 to be formed of amaterial having good moisture-resistant property, good surfacelubricating property, rubber elasticity, lower hardness than thatforming a recording surface of an optical recording medium, good heatresistant property, good chemical resistant property and good moldingproperty, and it is preferable to form the protective layer 19 ofthermoplastic polyether ester elastomer, silicon resin, fluorocarbonresin or the like.

FIG. 3 is a schematic cross-sectional view showing a main body of adrive.

As shown in FIG. 3, the detecting section 18 having the above describedconfiguration is disposed at such position that it can be brought intocontact with one surface of an optical recording medium by accommodatingthe tray 41 on which the optical recording medium is placed in the mainbody 40 of the drive and actuating the driving mechanism 17.

FIG. 4 is a set of schematic cross-sectional views showing various kindsof optical recording media, wherein FIG. 4( a) is a schematiccross-sectional view showing a CD type optical recording medium, FIG. 4(b) is a schematic cross-sectional view showing a DVD type opticalrecording medium and FIG. 4( c) is a schematic cross-sectional viewshowing a next-generation type optical recording medium.

As shown in FIG. 4( a), a CD type optical recording medium 20 a includesa substrate 21 a, a recording layer 22 a formed on the substrate 21 a, areflective layer 23 a formed on the recording layer 22 a and aprotective layer 24 a formed on the reflective layer 23 a, and thecentral portion of thereof is formed with a hole 25 a. In the thusconstituted CD type optical recording medium 20 a, a laser beam L20 ahaving a wavelength λ of 780 nm is projected thereonto from the side ofthe substrate 21 a, thereby recording data therein and reproducingrecorded therein.

The substrate 21 a serves to ensure the mechanical strength required bythe optical recording medium 20 a and an optical path for a laser beamL20 a is formed therein.

In the case where the optical recording medium 20 a is to be constitutedas a write-once optical recording medium (CD-R) or a data rewritabletype optical recording medium (CD-RW), grooves and/or lands are formedon the surface of the substrate 21 a. The grooves and/or lands serve asa guide track for the laser beam L20 a when data are to be recorded orwhen data are to be reproduced.

The substrate 21 a has a thickness of about 1.1 mm and is normallyformed of polycarbonate resin.

In the case where the optical recording medium 20 a is to be constitutedas a write-once optical recording medium (CD-R) or a data rewritabletype optical recording medium (CD-RW), the recording layer 22 a isformed.

In the case where the optical recording medium 20 a is constituted as awrite-once optical recording medium (CD-R), the recording layer 22 a isformed of organic dye and in the case where the optical recording medium20 a is constituted as a data rewritable type optical recording medium(CD-RW), the recording layer 22 a is constituted by a phase change filmand dielectric films sandwiching the phase change film.

In a write-once type optical recording medium, data are recorded in therecording layer. 22 a by transforming a predetermined region of organicdye contained in the recording layer 22 a. On the other hand, in a datarewritable type optical recording medium, data are recorded in therecording layer 22 a by changing the phase of the phase change filmcontained in the recording layer 22 a between a crystalline state and anamorphous state.

In the case where the optical recording medium 20 a is constituted as aROM type optical recording medium (CD-ROM), no recording layer 22 a isformed and data are recorded by pre-pits (not shown) formed on thesurface of the substrate 21 a when the optical recording medium 20 a isfabricated.

The reflective layer 23 a serves to reflect the laser beam L20 aentering via the substrate 21 a so as to emit it from the substrate 21 aand is formed so as to have a thickness of 10 to 300 nm.

The reflective layer 23 a is formed of metal such as aluminum, silver orthe like in order to effectively reflect the laser beam L20 a.

In this specification, a layer such as a reflective layer 23 a havingconductivity is sometimes referred to as “a conductive layer.” In thecase where the optical recording medium 20 a is constituted as a datarewritable type optical recording medium (CD-RW), since the material ofthe phase change film included in the recording layer 22 a normally hasconductivity, the recording layer 22 a falls in the category of “aconductive layer.”

The protective layer 24 a serves to physically and chemically protectthe recording layer 22 a. The protective layer 24 a is formed ofultraviolet ray curable resin or the like so as to have a thickness ofabout 100 μm.

In the thus constituted CD type optical recording medium 20 a, thedistance between the surface of the substrate 21 a through with thelaser beam L20 a enters and the reflective layer 23 a or the recordinglayer 22 a serving as a conductive layer is determined to be about 1.1mm.

On the other hand, as shown in FIG. 4 (b), the DVD type opticalrecording medium 20 b includes a first substrate 21 b, a recording layer22 b formed on the first substrate 21 b, a reflective layer 23 b formedon the recording layer 22 b, an adhesive layer 28 b formed on thereflective layer 23 b and a second substrate 26 b formed on the adhesivelayer 28 b, and the central portion of thereof is formed with a hole 25b. In the thus constituted DVD type optical recording medium 20 b, alaser bream L20 b having a wavelength λ of 650 nm is projected thereontofrom the side of the first substrate 21 b, thereby recording datatherein and reproducing recorded therein.

The first substrate 21 b serves to ensure the mechanical strengthrequired by the optical recording medium 20 b and the optical path ofthe laser beam L20 b is formed therein.

In the case where the optical recording medium 20 b is to be constitutedas a write-once optical recording medium (DVD-R) or a data rewritabletype optical recording medium (DVD-RW), grooves and/or lands are formedon the surface of the first substrate 21 b. The grooves and/or landsserve as a guide track for the laser beam L20 b when data are to berecorded or when data are to be reproduced.

The second substrate 26 b corresponds to the protective layer 24 a inthe CD type optical recording medium 20 a.

Each of the first substrate 21 b and the second substrate 26 b has athickness of about 1.1 mm and is normally formed of polycarbonate resin.

The recording layer 22 b is formed in the case where the opticalrecording medium 20 b is to be constituted as a write-once opticalrecording medium (DVD-R) or a data rewritable type optical recordingmedium (DVD-RW).

In the case where the optical recording medium 20 b is constituted as awrite-once optical recording medium (DVD-R), the recording layer 22 b isformed of organic dye and in the case where the optical recording medium20 b is constituted as a data rewritable type optical recording medium(DVD-RW), the recording layer 22 b is constituted by a phase change filmand dielectric films sandwiching the phase change film.

In the case where the optical recording medium 20 b is constituted as aROM type optical recording medium (DVD-ROM), no recording layer 22 b isformed and data are recorded by pre-pits (not shown) formed on thesurface of the first substrate 21 b when the optical recording medium 20b is fabricated.

The reflective layer 23 b serves to reflect the laser beam L20 bentering via the first substrate 21 b so as to emit it from the firstsubstrate 21 b and is formed so as to have a thickness of 10 to 300 nm.

The reflective layer 23 b is formed of metal such as aluminum, silver orthe like in order to effectively reflect the laser beam L20 b.

In the thus constituted DVD type optical recording medium 20 b, thedistance between the surface of the first substrate 21 b through withthe laser beam L20 b enters and the reflective layer 23 b or therecording layer 22 b serving as a conductive layer is determined to beabout 0.6 mm.

Further, as shown in FIG. 4( c), the next-generation type opticalrecording medium 20 c includes a substrate 21 c, a reflective layer 23 cformed on the substrate 21 c, a recording layer 22 c formed on thereflective layer 23 c and a light transmission layer 27 c formed on therecording layer 22 c, and the central portion of thereof is formed witha hole 25 c. In the thus constituted next-generation type opticalrecording medium 20 c, a laser bream L20 c having a wavelength λ ofabout 400 nm is projected thereonto from the side of the lighttransmission layer 27 c located on the opposite side from the substrate21 c, thereby recording data therein and reproducing recorded therein.

The substrate 21 c serves to ensure the mechanical strength required forthe optical recording medium 20 c and in the case where the opticalrecording medium 20 c is to be constituted as a write-once opticalrecording medium or a data rewritable type optical recording medium,grooves and/or lands are formed on the surface of the substrate 21 c.

Unlike in the CD type optical recording medium 20 a and the DVD typeoptical recording medium 20 b, in the next-generation type opticalrecording medium 20 c, no optical path of the laser beam L20 c is formedin the substrate 21 c.

The substrate 21 c has a thickness of about 1.1 mm and is normallyformed of polycarbonate resin.

The reflective layer 23 c serves to reflect the laser beam L20 centering via the light transmission layer 27 c so as to emit it from thelight transmission layer 27 c and is formed so as to have a thickness of10 to 300 nm.

The reflective layer 23 c is formed of metal such as aluminum, silver orthe like in order to effectively reflect the laser beam L20 c.

The recording layer 22 c is formed in the case where the opticalrecording medium 20 c is to be constituted as a write-once opticalrecording medium or a data rewritable type optical recording medium.

In the case where the optical recording medium 20 c is constituted as aROM type optical recording medium, no recording layer 22 c is formed anddata are recorded by pre-pits (not shown) formed on the surface of thesubstrate 21 c when the optical recording medium 20 c is fabricated.

The light transmission layer 27 c is a layer in which the optical pathof the laser beam L20 c is formed.

Although the thickness of the light transmission layer 27 c depends uponthe kind of the next-generation type optical recording medium 20 c, thelight transmission layer 27 c is formed so as to have a thickness ofabout 10 to 300 μm.

Although the material preferably used for forming the light transmissionlayer 27 c depends upon the kind of the next-generation type opticalrecording medium 20 c, a dielectric material such as ultraviolet raycurable resin, polycarbonate, polyolefin or the like is normallyemployed.

Owing to the configuration of the next-generation type optical recordingmedium 20 c in the foregoing manner, in the case where thenext-generation type optical recording medium 20 c is constituted as aROM type optical recording medium or a write-once optical recordingmedium, the distance between the surface of the light transmission layer27 c through with the laser beam L20 c enters and the reflective layer23 c serving a conductive layer is determined to be about 10 to 300 μm.On the other hand, in the case where the next-generation type opticalrecording medium 20 c is constituted as a data rewritable type opticalrecording medium, the distance between the surface of the lighttransmission layer 27 c through with the laser beam L20 c enters and therecording layer 22 c which is a conductive layer closest to the lighttransmission layer 27 c is determined to be slightly shorter than thedistance between the surface of the light transmission layer 27 c andthe reflective layer 23 c.

The apparatus 10 for discriminating an optical recording medium shown inFIGS. 1 to 3 discriminates the kind of an optical recording medium 20among the optical recording media having different structures in theabove described manner as follows.

FIG. 5 is a flow chart of a method for discriminating an. opticalrecording medium using the apparatus 10 for discriminating an opticalrecording medium.

In the case where the kind of an optical recording medium 20 is to bediscriminated using the apparatus 10 for discriminating an opticalrecording medium, the tray 41 of the drive is discharged from the mainbody 40 of the drive (Step S1) and an optical recording medium 20 isplaced on the tray 41 by the user (Step S2).

The tray 41 is then accommodated in the main body 40 of the drive (StepS3) and correspondingly, the detecting section 18 is moved upward inFIG. 3 by the driving mechanism 17 under the control of the controlcircuit 15 until the protective layer 19 comes into contact with thelight incidence plane of the optical recording medium 20 (Step S4).

As a result, as shown in FIG. 6, when the detecting section 18 has comeinto contact with the light incidence plane of the optical recordingmedium 20, substantially only the protective layer 19 is interposedbetween the light incidence plane of the optical recording medium 20,and the first electrode 11 and the second electrode 12.

At this time, since the surface of the protective layer 19 has goodlubricating property, the light incidence plane of the optical recordingmedium 20 is not damaged when the protective layer 19 comes into contactwith the light incidence plane of the optical recording medium 20.

Therefore, in the case where the optical recording medium 20 placed onthe tray 41 is a CD type optical recording medium 20 a, the distancebetween the first electrode 11 and second electrode 12 and thereflective layer 23 or recording layer 22, which is a conductive layer,becomes equal to (1.1 mm+thickness of the protective layer 19) and inthe case where the optical recording medium 20 placed on the tray 41 isa DVD type optical recording medium 20 b, the distance between the firstelectrode 11 and second electrode 12 and the reflective layer 23 orrecording layer 22, which is a conductive layer, becomes equal to (0.6mm+thickness of the protective layer 19).

On the other hand, in the case where the optical recording medium 20placed on the tray 41 is a next-generation type optical recording medium20 c, the distance between the first electrode 11 and second electrode12 and the reflective layer 23 or recording layer 22, which is aconductive layer, becomes equal to (10 to 300 μm+thickness of theprotective layer 19).

When the detecting section 18 comes into contact with the lightincidence plane of the optical recording medium 20 in this manner, acircuit shown in FIG. 7 is formed between the first electrode 11 and thesecond electrode 12.

In FIG. 7, C1 is a capacitance component constituted by the firstelectrode 11, the reflective layer 23 or the recording layer 22 and adielectric material present between the first electrode 11 and thereflective layer 23 or the recording layer 22, and C2 is a capacitancecomponent constituted by the second electrode 12, the reflective layer23 or the recording layer 22 and a dielectric material present betweenthe second electrode 12 and the reflective layer 23 or the recordinglayer 22. Here, C1=C2.

Therefore, the values of the capacitance components C1 and C2 aredetermined depending upon the thickness and dielectric constant of thedielectric material present between the first electrode 11 and secondelectrode 12 and the reflective layer 23 or recording layer 22. In thecase where the optical recording medium 20 placed on the tray 41 is a CDtype optical recording medium 20 a, they become equal to Ca and in thecase where the optical recording medium 20 placed on the tray 41 is aDVD type optical recording medium 20 b, they become equal to Cb, whereCb is larger than Ca. On the other hand, in the case where the opticalrecording medium 20 placed on the tray 41 is a next-generation typeoptical recording medium 20 c, they become equal to Cc, where Cc islarger than Cb.

Then, an alternating current signal A generated by the alternatingcurrent signal generation circuit 13 is applied to the first electrode11 under the control of the control circuit 15 while the detectingsection 18 is in contact with the light incidence plane of the opticalrecording medium 20 (Step S5).

As a result, since the alternating current signal A is transmitted tothe second electrode 12 via the circuit shown in FIG. 7, an alternatingcurrent signal B appearing at the second electrode 12 varies dependingupon the values of the capacitance components C1 and C2.

The alternating current signal B appearing at the second electrode 12 isdetected by the detection circuit 14 and the control circuit 15discriminates the kind of the optical recording medium 20 placed on thetray 41 based on the alternating current signal B detected by thedetection circuit 14 (Step S6).

More specifically, in the case where the level of the alternatingcurrent signal B is equal to that obtained when the values of thecapacitance components C1 and C2 are equal to Ca, the control circuit 15discriminates that the optical recording medium 20 placed on the tray 41is a CD type optical recording medium 20 a and in the case where thelevel of the alternating current signal B is equal to that obtained whenthe values of the capacitance components C1 and C2 are equal to Cb, thecontrol circuit 15 discriminates that the optical recording medium 20placed on the tray 41 is a DVD type optical recording medium 20 b. Onthe other hand, in the case where the level of the alternating currentsignal B is equal to that obtained when the values of the capacitancecomponents C1 and C2 are equal to Cc, the control circuit 15discriminates that the optical recording medium 20 placed on the tray 41is a next-generation type optical recording medium 20 c.

Therefore, if the range of the level of the alternating current signal Bto be obtained is obtained in advance for each kind of the opticalrecording media 20 and stored as a table 15 a in the control circuit 15,the kind of optical recording media 20 can be discriminated by referringto the table 15 a in the control circuit 15.

When the discrimination of the kind of the optical recording medium 20has been completed, the detecting section 18 is moved downward in FIG. 3by the driving mechanism 17 under the control of the control circuit 15so that the detecting section 18 is moved away from the light incidenceplane of the optical recording medium 20 (Step S7).

Thereafter, the optical recording medium 20 is rotated by a spindlemotor (not shown) (Step S8) and a laser component and an optical systemcorresponding to the kind of the optical recording medium 20discriminated at Step S6 are selected, thereby emitting a laser beamStep S9).

Then, an initial setting operation and the like are effected similarlyto in the conventional data recording and reproducing apparatus (drive)and data are recorded in the optical recording medium 20 or data arereproduced from the optical recording medium 20.

Therefore, if the apparatus for discriminating an optical recordingmedium according to this embodiment is mounted on a data recording andreproducing apparatus (drive), it is possible to immediatelydiscriminate the kind of an optical recording medium 20 set in the datarecording and reproducing apparatus prior to projecting a laser beamthereon.

According to this embodiment, since the kind of an optical recordingmedium 20 is discriminated while the detecting section 18 is in contactwith the surface of the optical recording medium 20, even in the casewhere an optical recording medium 20 to be discriminated is warped, itis possible to accurately discriminate the kind of the optical recordingmedium 20 without being affected by the warpage of the optical recordingmedium 20.

Therefore, according to this embodiment, even in the case where changein a detection signal caused by the warpage of an optical recordingmedium 20 greatly affects the results of discrimination of the kind ofan optical recording medium 20 such as when discriminating a DVD inwhich data are to be recorded in one layer on one side and a DVD inwhich data are to be recorded in two layers on one side, in which DVDsthe difference in distance between the light incidence plane and aconductive layers such as a reflective layer is small, the kind of theoptical recording medium 20 can nevertheless be accuratelydiscriminated.

Furthermore, according to this embodiment, since the kind of an opticalrecording medium 20 is discriminated by applying an alternating currentsignal A generated by the alternating current signal generation circuit13 to the first electrode 11 and detecting an alternating current signalB appearing at the second electrode 12 while the detecting section 18 isin contact with the surface of the optical recording medium 20, even inthe case of discriminating the kinds of next-generation type opticalrecording media that differ only slightly in the thickness and materialof the light transmission layers 27 c so that the values of thecapacitance components Cc are close to each other, the discriminationcan be made without being affected by an air layer having a highdielectric constant. Therefore, it is possible to accuratelydiscriminate the kind of a next-generation type optical recording medium20 by detecting the level of an alternating current signal B appearingat the second electrode 12.

Moreover, according to this embodiment, since the first electrode 11 andthe second electrode 12 are covered with the protective layer having agood lubricating property, it is possible to reliably prevent damage tothe light incidence plane of an optical recording medium 20 despite thefact that the protective layer comes into contact with the lightincidence plane of the optical recording medium 20.

Further, according to this embodiment, since the detecting section 18 ismoved away from the surface of an optical recording medium 20 by thedriving mechanism 17 after discriminating the kind of the opticalrecording medium and prior to rotating the optical recording medium 20by the spindle motor, it is possible to reliably prevent the detectingsection 18 from coming into contact with the surface of the opticalrecording medium 20 and damaging the optical recording medium 20 whenthe optical recording medium 20 is being rotated.

FIG. 8 is a schematic cross-sectional view showing one example of amethod for mounting the apparatus 10 for discriminating an opticalrecording medium on a data recording and reproducing apparatus (drive),wherein FIG. 8( a) shows the state where the tray 41 is discharged fromthe main body 40 of the drive and FIG. 8.(b) shows the state where thetray 41 is accommodated in the main body 40.

In this embodiment, when the tray 41 is discharged from the main body 40of the drive, as shown in FIG. 8( a), the detecting section 18 is movedto a position where it is in contact with the surface of an opticalrecording medium 20. On the other hand, when the tray 41 is accommodatedin the main body 40 of the drive, as shown in FIG. 8( b), the detectingsection 18 is moved away from the surface of an optical recording medium20.

Therefore, in the case where the apparatus 10 for discriminating anoptical recording medium is mounted on the data recording andreproducing apparatus (drive) in this manner, since it is possible todiscriminate the kind of an optical recording medium 20 after placingthe optical recording medium 20 on the tray 41 and prior toaccommodating the tray 41 in the main body 40 of the drive, the timerequired for recording data in or reproducing data from the opticalrecording medium 20 after it is placed on the tray 41 can beconsiderably shortened.

FIG. 9( a) is a schematic longitudinal cross-sectional view showinganother example of a method for mounting the apparatus 10 fordiscriminating an optical recording medium according to this embodimenton a data recording and reproducing apparatus (drive) and FIG. 9( b) isa schematic cross-sectional view taken along a line A—A in FIG. 9( a).

In this embodiment, a first electrode 11 and a second electrode 12 areconstituted by a shaft of a roller 43 of a slot-loading type datarecording and reproducing apparatus (drive).

The present invention has thus been shown and described with referenceto specific embodiments. However, it should be noted that the presentinvention is in no way limited to the details of the describedarrangements but changes and modifications may be made without departingfrom the scope of the appended claims.

For example, in the above described embodiments, although the kind of anoptical recording medium 20 is discriminated by employing the firstelectrode 11 and the second electrode 12 and detecting an alternatingcurrent signal B appearing at the second electrode 12 when analternating current signal A is applied to the first electrode 11, it ispossible to discriminate the kind of an optical recording medium 20 byemploying a planar-coil like electrode and detecting an eddy currentgenerated by supplying an electrical current to the planar-coil likeelectrode.

Further, in the above described embodiments, although the kind of anoptical recording medium 20 is discriminated while the detecting section18 is in contact with the light incidence plane of an optical recordingmedium 20, it is not absolutely necessary to discriminate the kind of anoptical recording medium 20 while the detecting section 18 is in contactwith the light incidence plane of an optical recording medium 20 and itis possible to discriminate the kind of an optical recording medium 20while the detecting section 18 is in contact with the surface of anoptical recording medium 20 opposite from the light incidence plane.

Furthermore, in the above described embodiments, although opticalrecording media in which focus distances are different from each otherare discriminated, the present invention can be applied to the casewhere a plurality kinds of optical recording media for which a commonrecording and reproducing system is used, for example, a DVD in whichdata are to be recorded in one layer on one side and a DVD in which dataare to be recorded in two layers on one side, are discriminated.

According to the present invention, it is possible to provide anapparatus for discriminating an optical recording medium and a methodfor discriminating an optical recording medium which can reliablydiscriminate the kind of an optical recording medium.

Further, according to the present invention, it is possible to providean apparatus for discriminating an optical recording medium and a methodfor discriminating an optical recording medium which can reliablydiscriminate the kind of an optical recording medium even in the casewhere the optical recording medium to be discriminated is warped.

1. An apparatus for discriminating an optical recording medium comprising at least a first dielectric layer, a second dielectric layer and a conductive layer formed between the first dielectric layer and the second dielectric layer, the apparatus for discriminating an optical recording medium comprising a detecting section provided with an electrode, a first means for applying a signal for detection to the electrode and a second means for bringing the detecting section into contact with a surface of the first dielectric layer.
 2. An apparatus for discriminating an optical recording medium in accordance with claim 1, wherein the detecting section further comprises a protective layer for covering a surface of the electrode and the second means is constituted so as to bring the protective layer of the detecting section into contact with the surface of the first dielectric layer.
 3. An apparatus for discriminating an optical recording medium in accordance with claim 1, wherein the second means is constituted so to set the detecting section apart from the surface of the first dielectric layer prior to rotating an optical recording medium.
 4. An apparatus for discriminating an optical recording medium in accordance with claim 2, wherein the second means is constituted so to set the detecting section apart from the surface of the first dielectric layer prior to rotating an optical recording medium.
 5. An apparatus for discriminating an optical recording medium in accordance with claim 3, wherein the detecting section is provided in a tray of a drive and the second means is constituted so as to move the detecting section in synchronism with discharge and accommodation of the tray.
 6. An apparatus for discriminating an optical recording medium in accordance with claim 4, wherein the detecting section is provided in a tray of a drive and the second means is constituted so as to move the detecting section in synchronism with discharge and accommodation of the tray.
 7. An apparatus for discriminating an optical recording medium in accordance with claim 1, wherein the first dielectric layer is constituted as a light transmittance layer and the second dielectric layer is constituted as a substrate.
 8. An apparatus for discriminating an optical recording medium in accordance with claim 2, wherein the first dielectric layer is constituted as a light transmittance layer and the second dielectric layer is constituted as a substrate.
 9. An apparatus for discriminating an optical recording medium in accordance with claim 3, wherein the first dielectric layer is constituted as a light transmittance layer and the second dielectric layer is constituted as a substrate.
 10. An apparatus for discriminating an optical recording medium in accordance with claim 4, wherein the first dielectric layer is constituted as a light transmittance layer and the second dielectric layer is constituted as a substrate.
 11. An apparatus for discriminating an optical recording medium in accordance with claim 5, wherein the first dielectric layer is constituted as a light transmittance layer and the second dielectric layer is constituted as a substrate.
 12. An apparatus for discriminating an optical recording medium in accordance with claim 6, wherein the first dielectric layer is constituted as a light transmittance layer and the second dielectric layer is constituted as a substrate.
 13. An apparatus for discriminating an optical recording medium in accordance with claim 1, wherein the electrode is constituted by a shaft of a roller of a slot-loading mechanism.
 14. An apparatus for discriminating an optical recording medium in accordance with claim 2, wherein the electrode is constituted by a shaft of a roller of a slot-loading mechanism.
 15. An apparatus for discriminating an optical recording medium in accordance with claim 3, wherein the electrode is constituted by a shaft of a roller of a slot-loading mechanism.
 16. An apparatus for discriminating an optical recording medium in accordance with claim 4, wherein the electrode is constituted by a shaft of a roller of a slot-loading mechanism.
 17. An apparatus for discriminating an optical recording medium in accordance with claim 5, wherein the electrode is constituted by a shaft of a roller of a slot-loading mechanism.
 18. An apparatus for discriminating an optical recording medium in accordance with claim 6, wherein the electrode is constituted by a shaft of a roller of a slot-loading mechanism.
 19. An apparatus for discriminating an optical recording medium in accordance with claim 7, wherein the electrode is constituted by a shaft of a roller of a slot-loading mechanism.
 20. A method for discriminating an optical recording medium comprising at least a first dielectric layer, a second dielectric layer and a conductive layer formed between the first dielectric layer and the second dielectric layer, the method for discriminating an optical recording medium comprising steps of bringing a detecting section having an electrode into contact with a surface of the first dielectric layer and applying a signal for detection to the electrode, thereby discriminating the kind of the optical recording medium. 